Method of loading a hopper of a suction dredger with sand

ABSTRACT

In loading a hopper of a floating suction dredger with sand a suspension of sand and water is pumped into the hopper. After the hopper is filled up to its maximum permissible carrying capacity in a first loading step additional suspension is pumped into the hopper in a second loading step during simultaneously draining off by lowering drain means in dependence on the weight of the load of the hopper for maintaining the suction dredger substantially loaded at its maximum permissible carrying capacity.

United States Patent Inventor Jan De Koning Amsterdam, Netherlands App1.No. 874,212 Filed Nov. 5, 1969 Patented Dec. 28, 1971 Assignee N.V. lngenieursbureau voor Systemen en Octrooien Spanstaal, Binnenweg, Rotterdam, Netherlands Priority Nov. 8, 1968 Netherlands 68.15921 METHOD OF LOADING A HOPPER OF A SUCTION DREDGER WITH SAND 2 Claims, 8 Drawing Figs.

U.S. Cl 214/152, 37/58, 114/26, 137/403, 137/579, 210/83, 210/242, 214/15 B Int. Cl B63b 27/00 Field of Search 302/14, 58;

114/26, 76, 73; 37/58, 59; 137/403, 579, 578; 210/83, 84,1l3-1l5,242;2l4/1214,152,15,15 B, 15 D References Cited UNITED STATES PATENTS McDougall Van Den HaspeL.

Munro Ewig... Miller.

Chase..... Pregno Primary ExaminerGerald M. Forlenza Assistant Examiner-Frank E. Werner Almrneylmirie, Smiley, Snyder and Butrum ll4/26X 2l4/15BX 210/113 214/15B 37/58 UX 210/83 137/578 ABSTRACT: In loading a hopper of a floating suction dredger with ,sand a suspension of sand and water is pumped into the hopper. After the hopper is filled up to its maximum permissible carrying capacity in a first loading step additional suspen sion is pumped into the hopper in a second loading step during simultaneously draining off by lowering drain means in dependence on the weight of the load of the hopper for maintaining the suction dredger substantially loaded at its maximum permissible carrying capacity.

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INVENTOR JAN a mums BY LL LJA,- L1MR ATTORNEYS METHOD OF LOADING A HOPPER OF A SUCTION DREDGER WITH SAND The invention relates to a method of loading a hopper of a floating suction dredger with sand.

Such a method is known.

In this known method a suspension of sand and water is pumped into the hopper in a first step. When the hopper is completely filled, the hopper contains only a little amount of sand. In a second step additional suspension is pumped into the hopper during. simultaneously draining off until the amount of sand does not increase anymore.

The settling of sand depends on the size of the grains and the flow velocity of the suspension. In a given hopper cross section the free flow area above the settled sand decreases as sand settles, resulting in an increase of the flow velocity of the suspension up to a value preventing further settlement of sand. At this value of the flow velocity of the suspension pumped into the hopper this suspension is drained off with all its sand. The quotient of the sand volume and the hopper volume, which sand volume can be reached with a given grain size of the sand, a given capacity of the pump and a given hopper cross section is called the bulking factor.

As the specific gravity of wet sand is about 2, the hopper of the known suction dredger has a volume in m substantially equal to half its maximum permissable carrying capacity.

As such hopper cannot be filled completely with sand owing to said bulking factor it has been proposed already providing the hopper with an upstanding upper edge comprising draining off flaps, for loading the hopper with a little more sand owing to the increased free flow area above the settled sand. In a third loading step during which no suspension is pumped into the hopper, sand is allowed to settle. After that the water is drained off by suddenly lowering the draining off flaps. This third loading step may be reproduced.

The invention has the object to shorten the loading time. To this aim the invention provides a method of loading a hopper of floating suction dredger with sand, wherein a suspension of sand and water is pumped into the hopper during a loading operation carried out in at least two steps:

a first step of pumping suspension into the hopper until the suction dredger is loaded substantially up to its maximum permissable carrying capacity,

and a subsequent second step of pumping additional suspension into the hopper during simultaneously draining off by lowering drain means in dependence on the weight of the load of the hopper for maintaining the suction dredger substantially loaded at its maximum permissable carrying capacity.

Further the invention provides a floating suction dredger comprising a hopper and a pump for pumping suspension of sand and water into said hopper, characterized by load-measuring means controlling adjustable drain means.

The invention further has the object to load the floating suction dredger suction dredger up to its maximum permissable carrying capacity with sand. To this aim the volume of the hopper is so great, that the suction dredger is loaded up to its maximum permissable carrying capacity when the hopper is substantially completely filled with sucked up suspension of sand and water.

If the sucked up suspension has a specific gravity of about 1.2 the hopper is filled only up to percent with sand at the end of the first step, while than no suspension may be pumped into the hopper anymore for preventing that the maximum permissable carrying capacity of the suction dredger will be exceeded. Therefore in the second step of the method according to the invention the drain means are put in operation as soon as the suction dredger is loaded up to its maximum permissable carrying capacity during simultaneously pumping of additional suspension into the hopper.

For safety the drain means preferably have a capacity exceeding the pump capacity.

Preferably the drain means comprise at least one drain siphon having a depth-adjustable inlet.

For safety the floating suction dredger according to the invention preferably comprises a safety device which is controlled by load-measuring means and which becomes operative when the weight of the load of the hopper exceeds a predetermined value. This safety device may actuate an alarm device, may put the pump out of working and/or may in case of emergence put in operation unloading means for discharging sand from the hopper.

It is an additional advantage that owing to the floating suction dredger being loaded in a short time up to its maximum permissable carrying capacity the pump of the suction dredger is lowered to a great extent relatively to the water level immediately after starting the loading operation, resulting in increase of suction force of said pump of about 1 M water column.

The mentioned and other features according to the invention will be illucidated in the following description with reference to the accompanying drawing.

FIG. la and lb show graphs of the known method for loading a known suction dredger.

FIG. 1c shows a cross section of said known suction dredger,

FIG. 2a and 2b show graphs of the method according to the invention for loading a suction dredger,

FIG. 3 shows a longitudinal section of a preferred embodiment of a suction dredger according to the invention,

FIG. 4 shows a plan view of the suction dredger of FIG. 3 and FIG. 5 shows diagrammatically the control and safety devices of the suction dredger of FIGS. 3 and 4.

In FIGS. la and 2a interrupted lines show the suspension volume and uninterrupted lines show the sand weight at any time during loading operation.

In FIGS. lb and 2b interrupted lines show the suspension weight and uninterrupted lines show the sand weight at any time during loading operation.

In comparing the method according to the invention with the known method, FIGS. 1 and 2 are based on equal maximum permissable carrying capacities of the suction dredgers and on equal suspension flows which can bepumped into the hopper, said suspension flows having equal rates of sand.

For conveying a volume V of wet sand (FIG. 1a) in the known method a suction dredger is applied having a maximum hopper volume V,,, which can be reduced by lowerable draining ofi flaps 6 to a volume V,, In carrying out the known method, suspension is pumped into the hopper 2 of the suction dredger 1 of FIG. lc during a first-loading step 3 starting at the point of time 0 and ending at the point of time A at which the hopper 2 is completely filled up to its upper edge 5. The hopper 2 has draining off flaps 6 being closed during the firstloading step 3. In this first-loading step 3 the volume V and also the weight G increase considerably. During the subsequent loading step 4 in the period AD suspension is continuously pumped into the hopper 2, liquid being drained off to an equal extent. The rate of sand of this drained off liquid increases gradually. The volume of sand settling per time unit is so little at the point of time D, that continuation of the secondloading step 4 is not efficient anymore. For this reason the operation of pumping sand into the hopper 2 is stopped and during a third-loading step 7 the sand of the suspension is allowed to settle. At the point of time B the draining off flaps 6 are lowered into the draining off position 6', for draining off the upper water. The hopper volume is than V, In a subsequent fourth-loading step 8 the draining off flaps 6 are closed and the hopper 2 is filled with additional suspension in the period FIG. In the period GH the sand of the suspension is allowed to settle, during which period no suspension is pumped into the hopper 2. At the point of time II the required sand volume V is obtained.

In FIGS. 3 and 4 a floating suction dredger for carrying out the method according to the invention is shown. This suction dredger consists of a trailing suction dredger having a hopper 12, a pump 10 connected to a trailing suction pipe 9 at its suction side and to a supply pipe 15 at its pressure side and having swingable draining off siphons 16 forming draining off means...

Each draining off siphon 16 comprises a fixed siphon pipe 41 connected to a pipe 20 and through a flexible conduit 42 to a movable siphon pipe 41 pivotably mounted at the siphon pipe 41. The movable siphon pipe 41 is operated by means of a hydraulic jack 17 and has an inlet nozzle 43. In the bottom of the hopper 12 sand outlets 18 are provided with discharge valves 19.

The hopper 12 could be divided into two longitudinal parts. The suction dredger could comprise two hoppers 12 arranged behind each other.

The operation for loading this suction dredger 11 is as hereinafter described:

In a first-loading step 13 suspension sucked up through the suction pipe 9 is pumped by the pump 10 through the supply pipe into the hopper 12 until the suction dredger 11 is loaded up to its maximum permissable carrying capacity.

The hopper 12 now contains sand and water of which sand a volume V has been settled at the point of time B. The draining off siphons 16 now are still in the position 16,.

In the subsequent second-loading step 14 additional suspension is pumped into the hopper 12, and the draining off siphons 16 are lowered into the hopper 12 to such depth, that so much liquid is drained off through said draining off siphons l6 and the pipes 20 connected thereto into the outboardwater 21, that the suction dredger is maintained loaded at its maximum permissable carrying capacity. The draining off siphons 16 are gradually lowered from the position 16, into the posi tion 16,.

FIG. 2 clearly shows, that the total required loading time 0C of the loading steps 13 and 14 of the method according to the invention is considerably less than the total required loading time OH of the known method, whereas the sand volume V is about equal to the sand volume V of FIG. 1. The

or qad ast me sa ea t 9 the as! tsite v in which the suction dredger is continuously loaded up to its maximum permissable carrying capacity. The total weight then continuously maximum (see FIG. 2b), whereas the total weight W, in FIG. lb increases gradually during the second-loading step 4, but is maintained under the maximum value of W,. V 0......

The load is measured with pressure pick ups 22,, 22 and 22, each arranged at the bottom of the suction dredger 11 and each comprising a pressure sensitive membrane 33, limiting a chamber 24 connected to the outboardwater 21. Each pressure pickup 22,, 22 and 22, picks up the pressure corresponding with its depth in the outboardwater, which is a measure for the draught of the suction dredger 11 and the weight of the load. Nine pressure pickups 22,, 22, and 22, are provided: at port board, in the longitudinal center plane and at starboard respectively as well as at the front, the rear and the midpart of the suction dredger.

Preferably in the second-loading step 14 at each load situation the corresponding hopper'volume is adjusted automatically, for maintaining the suction dredger loaded at its maximum permissable carrying capacity.

In FIG. 5 the automatic control means for carrying out the method according to the invention are shown diagrammatically.

The pressure pickups 22,, 22, and 22, provide signals to receivers 25,, 25, and 25, respectively. From these signals the draughts of the corresponding ship parts are determined in calculating units 26,, 26, and 26,. The outputs of these calculating units are provided to the draught-, list-and trim-calculating unit 27, providing signals to the draught indicator 28, trimindicator 29 and the safety device 30, the calculating unit 26, providing signals concerning the starboard draught to the comparing and calculating device 31, which in turn provides signals to the signal converters 32,. These signal converters 32, provide signals to the control valves 33, for controlling the hydraulic jack 17, of the draining off siphon 16,. Calculating unit 31, provides signals concerning the central draught to both signal converters 32, and 32,, whereas calculating unit A, in the same way provides signals to signal converter 32, and thus operates the jack 17, of draining off sip hon 16,.

As the calculating device 31 signals like reference signals to both signal converters 32, and 32,, the list of the suction dredger owing to unequally loading may be corrected.

In case of an overloading and/or an inadmissible list, which is insufficiently corrected by the above-mentioned automatic control signals through calculating devices 31,, 31, and 31,. the safety device 30 provides signals to an alarm device 34 formed by a red light, an accoustic alarm device 35 and to an automatic safety unit 36 providing signals for lowering the draining off siphons 16, and 16, through signal converters 32, and 32,, signals for putting the pump 10 out of work through signal converter 37 and signals for opening the sand discharge valves 19 through signal converter 38.

In order, however, to maintain the suction dredger 11 in operation when the automatic control means are out of order, the draining off siphons 16, and 16,, the pump 10, and the discharge valves 19 may be controlled from an operating panel by hand through the hand operated members 40,, 40, and 39.

Owing to the application of a plurality of load sensitive elements, formed by a plurality of pressure pickups 22 the lack of indication of the exceed of the maximum permissable carrying capacity is prevented.

When sucking up a suspension having a low rate of sand, the hopper 12 which has a great volume, may be completely filled, although the suction dredger is not yet loaded up to its maximum permissable carrying capacity. In this case suspension is still pumped into the hopper, during a period in which the draining off siphons are kept in their positions 16,, and in which liquid mainly consisting of water is drained off over the upper edge 44 of the hopper 12. When the suction dredger is loaded up to its maximum permissable carrying capacity in this way, additional suspension is pumped into the hopper 12 in the second-loading step 14, in which liquid is drained off by lowered draining off siphons 16 which are adjusted in dependance on pressure pickups 22 so that the suction dredger is maintained loaded at its maximum permissable carrying capacity.

At the end of the second-loading step 14 the pump 10 is put out of work and the sand in the suspension standing above settled sand is allowed to settle in a subsequent period, at the end of which the water standing above all settled sand is drained off by lowering the draining off siphons up to the surface of sand. In this way the suction dredger is even loaded less than its maximum permissable carrying capacity during the trip to the unloading place.

The suction dredger 11 preferably comprises a water pump 45 pumping up outboardwater 21 through inlet pipe 46 and being connected by conduits 47 to jet-nozzles 48 mounted in the siphon pipes 41. These jet nozzles function like jet pumps for starting the siphon operation of the draining off siphons 16, when necessary.

It should be remarked, that at the point of time C the pump 10 is put out of work and that the trip to the unloading place can be started. In the subsequent period 49 over the time CD the sand found in the suspension above settled sand settles. At the point of time D all liquid standing above settled sand is drained off, resulting in a suction dredger which is loaded less than its maximum permissable carrying capacity during the remaining time of this trip, resulting in a greater speed of the suction dredger.

If the level of the settled sand is lower than the water surface of outboardwater the liquid above the settled sand may be drained off owing to the jet nozzles 48 operating like jet pumps. After draining off operation the draining off siphons are raised into their uppermost position.

What I claim is:

1. Method of loading a hopper of a floating suction dredger with sand, wherein a suspension of sand and water is pumped into the hopper during a loading operation carried out in at least two steps:

a first step of pumping suspension into'the hopper until the suction dredger is loaded substantially up to its maximum permissable carrying capacity,

LII

capacity.

2. Method as claimed in claim I, wherein the second step is carried out until the suction dredger is loaded with substantially sand at its maximum permissable carrying capacity.

t i I i 

1. Method of loading a hopper of a floating suction dredger with sand, wherein a suspension of sand and water is pumped into the hopper during a loading operation carried out in at least two steps: a first step of pumping suspension into the hopper until the suction dredger is loaded substantially up to its maximum permissable carrying capacity, and a subsequent second step of pumping additional suspension into the hopper during simultaneously draining off by lowering drain means in dependence on the weight of the load of the hopper for maintaining the suction dredger substantially loaded at its maximum permissable carrying capacity.
 2. Method as claimed in claim 1, wherein the second step is carried out until the suction dredger is loaded with substantially sand at its maximum permissable carrying capacity. 